The goal of this research is to develop a self-performing, one-step, semi-quantitative, visual immunometric assay for human TSH. This assay will use whole blood as a substrate and indicate whether serum levels of TSH in excess of 5 IU/ml are present. It will contain a built-in control to indicate successful assay completion. This assay will be helpful as a screen for neonatal hypothyroidism, especially in populations that lack the technological infrastructure required to perform currently available TSH assays. It will also be used to screen samples in a cost-effective fashion for the presence of an elevated TSH and thus indicate whether a sample requires a more expensive quantitative TSH assay. By allowing TSH measurement to be performed outside of a laboratory and by providing a screening method o detect an elevation in TSH, this assay represents a significal technical innovation. Because of its low cost and ease of use, it will have considerable commercial application as a replacement for more expensive and cumbersome radio-, enzyme-linked, fluorescent, and chemiluminescent immunoassays.